Optimal fetal growth is recognized as the basic foundation for lifelong health; both growth restriction and excess fetal growth are associated with infant, child, and adult morbidity and mortality. Identifying abnormal fetal growth early enough to allow for clinical intervention and mitigation of the associated maternal and neonatal risk depends on the availability of appropriate growth charts with which to compare fetal biometric measurements. There have been two recently published fetal growth standards (designed to represent optimal growth); one by INTERGROWTH-21st and another by the World Health Organization (WHO). Questions have been raised, however, about their applicability and clinical utility for all population groups based on marked variation in fetal growth according to ethnicity and the creation of the standards using measurements from healthy women, in optimal conditions, who may be unrepresentative of the broader pregnant population. Responding to this debate, this proposal aims to develop fetal growth references for Samoans, which reflect usual growth and may therefore avoid some of the potential misclassification of both growth restriction and excess fetal growth associated with the standards. Until now, Pacific Islanders, including Samoans, have been extremely underrepresented in the construction of publicly available growth charts despite their markedly poorer perinatal outcomes compared with the general US population. Our specific aims are: (1) to develop and validate population-specific growth references for Samoans; (2) to (a) compare the Samoan-specific fetal growth references against the WHO and INTERGROWTH-21st standards and (b) explain any systematic differences between growth charts; and (3) to compare the diagnostic ability of the Samoan-specific fetal growth references against the WHO and INTERGROWTH-21st standards for perinatal and childhood obesity outcomes. The innovation in this proposal lies in our focus on a Pacific Islander population, the fact that we will be among the first to test the diagnostic and predictive ability of the very recently published WHO standards in a traditionally underrepresented population group, and our focus on predicting both perinatal and childhood- obesity related outcomes using fetal growth references. While the connection between fetal growth and later cardiometabolic risk is well established, few studies have explored the utility of fetal growth trajectories as a potential biomarker for later metabolic risk. We expect the construction of an ethnicity-specific fetal growth reference to improve clinical detection of fetal growth abnormalities, allow earlier management, and therefore improve perinatal outcomes among Samoans. In addition, increased detection of childhood-obesity risk, allowing for early preventative intervention, stands to have a significant public health impact for this population.